FMTV Do You Leave your Cab Air Springs / Leveler Engaged?

I was wondering if people leave their cab air springs engaged (auto leveling) when they are not operating their trucks or do you release the knob at the manifold control box?

Thanks!

OD

I leave it on all the time. I suppose the cab droops down at some point when the system air leaks out. I wonder if it make a sound if nobody is there to hear it?

I don't touch mine either.

OK. Thanks for the info I guess I will turn it on and leave it there. Do you switch it off when raising/lowering the cab?

OD

I only touch mine once in awhile, just to make sure it works. I usually check it when I'm at the controls.

Ok, thanks all for your feedback. I am assuming that you release the auto level knob when you raise/lower the cab.

Thanks!

OD

Hi OD,

I never fool with the system either, leaving the air suspension 'on' all the time. Is there some reason you have concern about status of the cab suspension system when raising the cab? When the truck is shut down, as air bleeds down the cab does settle (but usually air bleeds very slowly).

Bob

Bob,
Yea I was concerned about leaving it on all the time and all the air bleeding out but I guess that is no big deal since you should drain your tanks if going to sit anyway. I was just wondering if you turn off the valve when raising or lowering the cab if there is a potential for damage or issues.

I will not worry about it anymore and just engage the auto-level and forget about it...

Thanks!

OD

Hi OD,

I wondered about mine, too, when first using the truck. Once the cab was raised and lowered a few times, and the latch assembly had no trouble with alignment as it settled into the cradle, I promptly forgot about it. BTW, There should be no more air leakage from the suspension system engaged as not.

Hi,

I found this thread while searching for information to help me understand a confusing statement in the operator's manual, TM 9-2320-365-10. On page 2-373 is says "Caution: Do not operate vehicle off-road without both air springs unpinned and deflated. failure to comply may result in damage to equipment." Does anybody understated this? Seems very counter-intuitive to me. Am I completely missing something here???

-Walt

Waltjg said:

Hi,

I found this thread while searching for information to help me understand a confusing statement in the operator's manual, TM 9-2320-365-10. On page 2-373 is says "Caution: Do not operate vehicle off-road without both air springs unpinned and deflated. failure to comply may result in damage to equipment." Does anybody understated this? Seems very counter-intuitive to me. Am I completely missing something here???

-Walt

Click to expand...

well it was written by a engineer...

I noticed the pin mount holes in the air spring base on mine. The pins are missing with just the wire holders dangling there. Will fire up the TM in the morning and do some reading.

Shadowrwolf,
I am looking at the -10 on page 2-373 and I see exactly what you are referring to. The weird thing is that this page as well as 2-375 which talks about changing CTIS settings are right in the middle of the 2-58. PREPARATION FOR INTERNAL AIR TRANSPORT (CONT) instructions. Almost like they are in the incorrect sequence in the TM. So, I don't have an answer to your question. Reading the page tells me not to have the air springs engaged or pinned while going off road but that seems counterintuitive. I guess my other concern would be if those pins are required during normal operation in one of the positions they go in... As I said before I am missing both pins for the air springs.

Are we talking about the cylinder on each side with a piece of chain and adapter mounted to it. If so, those are not for the cab. They are to compress the suspension and the pins on those are to hold it there once the air bleeds off to keep the suspension compressed. This is done in addition to using the CTIS to lower the height of the truck to fit into cargo aircraft.

Sandcobra164, no we are talking about the cab air springs and the holes and pins at the bottom of the brackets that the air springs sit in.

That statement in the manual makes sense if you consider that when off road the frame may flex, and the cab mounting has to follow. Flexing a cab is never a good idea. If the support frame were pinned, the cab on the FMTV could get tweeked even though it does have a pivoting mount in the rear. If the frame twists, the rear of the cab would try to move back and forth a little with respect to the frame at the support frame ends. Unpinning the cab support frame, and deflating the lift bladders would provide the most movement to the rear of the cab.

I get my LMTV twisted up often here on the farm and it sure does creak and groan. Maybe I can see how much the rear of the cab wanders around.

Bob

Thank you Bob. That does make sense. I could tell by examining the assembly that not having the pins in during operation made sense. What I couldn't understand, was why deflate the cab suspension when, seemingly, you'd want it most--off road.

Now I just wonder why the pins are there at all (though this is a separate and unimportant concern really). They look to make a rigid connection b/w each side of the cab and the frame, which I cannot imagine when would ever be desirable...

But back to my original concern--so, the winning answer is deflating the cab suspension allows for the most movement b/w cab/frame; and the cab air springs should indeed be deflated when operating on uneven ground?

Thanks again,
Walt

My pins are stowed, the knob pushed in and locked since I got it, I drove it today with it deflated...the cab was all overs the place it seemed. I pulled over and infated them, rides much nicer on the road...IMO. So I'm going to leave them inflated.

Is the stowed position directly under the bags? My pins are missing.

I would think the issue off-road is bouncing and jittering all over the place so the little level sensor would be trying to level the cab constantly.

Correct, the stowed hole for the pin in below the spring. Actively pinned would be through the hole in the actuating (upper) part of the spring as well as thru the collar at the base of the. spring assy. These pinned holes face you as you look at the spring
View attachment TM 9-2320-365-10 page 2-373.pdf